Abdominal exercises are useful for building the abdominal muscles. This is useful for improving performance with certain sports, back pain, and for withstanding abdominal impacts (e.g., taking punches). According to a 2011 study, abdominal muscle exercises are known to increase the strength and endurance of the abdominal muscles.[1]

It has been highly disputed whether or not abdominal exercises have any reducing effect on abdominal fat. The aforementioned 2011 study found that abdominal exercise does not reduce abdominal fat; to achieve that, a deficit in energy expenditure and caloric intake must be created—abdominal exercises alone are not enough to reduce abdominal fat and the girth of the abdomen.[1] Early results from a 2006 study found that walking exercise (not abdominal exercise specifically) reduced the size of subcutaneous abdominal fat cells; cell size predicts type 2 diabetes according to a lead author. Moderate exercise reduced cell size by about 18% in 45 obese women over a 20-week period; diet alone did not appear to affect cell size.[2]

Abdominal muscles have many important functions, including in breathing, coughing, and sneezing, and maintaining posture and speech in a number of species.[3] The anterior abdominal wall is made up of four muscles—the rectus abdominis muscle, the internal and external obliques, and the transversus abdominis."The two internal muscles, the internal oblique and the transverse abdominis, respond more to increases in chemical or volume-related drive than the two external muscles, the rectus abdominis and external oblique; the basis for this differential sensitivity is unknown".[3]

Not only can one-sided preference for abdominal muscles (lack of exercise focused on other core muscles) result in creating muscle imbalances, but the effectiveness of exercise is also far from what could be achieved with a balanced workout planning. Core training frequently utilizes balance exercises. These are characterized by unstable position that requires involvement of a wide range of muscles which help balance oscillation of the centre of gravity. We can balance both in static positions and while performing dynamic movements.[citation needed]

The goal of core training is definitely not to develop muscle hypertrophy but to improve functional predispositions of physical activity. This particularly involves improving intra- and intermuscular coordination or synchronization of participating muscles.

Involvement of the core means more than just compressing abdominal muscles when in crouching or seated position. The role of the core muscles is to stabilize the spine. Resisting expansion or rotation is as important as the ability to execute movement.

The abdominal muscles can be worked out by practicing disciplines of general body strength such as Pilates, yoga, T'ai chi, and jogging among others.[according to whom?] There are also specific routines to target each of these muscles.

One way to estimate the effectiveness of any abdominal exercise is in measuring the momentaneous[jargon] activity by electromyography (EMG), with the activity generally being compared to that of the traditional crunch. However, an exercise of lower activity performed during a longer time can give at least as much exercise as a high-activity exercise, with the main difference being that a prolonged duration results more in aerobic exercise than strength training.

The following tables rank abdominal exercises from highest to lowest in terms of activity as determined by the EMG measures:[4]

The bicycle targets the rectus abdominals and the obliques. Also, the rectus abdominals can be worked out with the basic crunch, the vertical crunch, the reverse crunch, and the full vertical crunch, and when at a low enough body fat percentage (10-12% for males, 15-18% for females) the individual parts of the muscle become visible; many refer to this visible separation as a six pack. By exercising the internal and external obliques the stomach can be flattened while the waist line can be reduced.[5] The long arm crunch, in which arms are straightened behind you, adds a longer level to the move and emphasizes the upper part of the abs. The plank exercise not only strengthens the abs but also the back and stabilizes the muscles.[6]

Abdominal exercises can also be performed with the help of some machines and the captain's chair is one of the most popular machines used in gyms and health clubs. Other machines are the Ab Roller, the Ab Rocket Twister, the Chin-up bar in conjunction with Ab Straps and the Torso Track. The exercise ball is also a tool that helps strengthen the abs. It may be more effective than the crunches on the floor because the abs do more work as the legs are not involved in the exercise.[7] With respect to the Ab-Slide, the study performed by Bird et al. showed greater muscle activation in the upper rectus abdominis, lower rectus abdominis, and external oblique when compared to the standard abdominal crunch. The Ab-Slide has proven to be an effective tool in strengthening the abdominal muscles from a concentric muscle action perspective. However, this research does not support replacing the traditional crunch exercise with the Ab-Slide gadget due to the lack of proven effectiveness in the eccentric loading of the abdominal muscles and the greater postural control.[8][9] Potentially the most effective equipment for abdominal strengthening are those that offer the least stability. Examples include the CoreFitnessRoller, bodyweight suspension training such as TRX and stability balls with or without the Halo.

Abdominal exercises also put some degree of compressive force on the lumbar spine, putting unwanted stress on the lower back. In addition, exaggerated abdominal exercise can cause respiratory problems.[10] A study of twelve exercises concluded that no single exercise covered all abdominal muscles with high intensity and low compression.[11]